how much amp does a sf kl4 draw?

how much amp does a surefire kl4 head draw?

reason i ask is because i have the head on a vital gear fb1 (1 cell) body, and when using 1x protected rcr123; it'll flash once and just turn off

but when using unprotected rcr123, it'll power that sucker (the kl4 head) like the sun!

i also understand that protected rcr123's will cut off power at certain high voltage points (or whatever the correct term is), whereas unprotected cells will just feed power


so back to my questions: how much amp does a sf kl4 draw?

and while we're at this topic, whats the estimated runtime using 880mah cell running a kl4 head?

Hmm, that doesn't sound right. I don't know how much amps it draws but I believe the KL4 is under driven. I've had about 5 different KL4 heads at one time or another and never had a problem with protected batteries.

I think my KL4 pulls about an amp and a half from a single li-ion cell (3.7~4.2 volts).

It all depends on the forward voltage of the LED. I have seen KL4's draw 1.25A all the way up to 1.9A from a power supply set to 3.8V. Those Vitalgear switches are probably not made for that amount of current. Whoever designed (or should I say, selected) the switch in the Vitalgear was not very technical and put in a real wimpy switch designed for low current applications.

I measured my L4 once with 2x 3.0V RCR123's: 1.05 Amps
VG FB1 with 3.7V RCR123 works at full power, with an 3.0 rechargeble or primary cell it gives lower output.

Errr..you DO know that 8.4V will kill the thing sooner or later, right?
Mine draws 1.1amps on a single li-ion

GarageBoy said:

Errr..you DO know that 8.4V will kill the thing sooner or later, right?

Click to expand...

Talkin' to me? I use 3.0V RCR123's which voltage drops to 3.0V when under load. I measured it. Works fine in my L4 for about 1 year.

Xygen said:

I measured my L4 once with 2x 3.0V RCR123's: 1.05 Amps
VG FB1 with 3.7V RCR123 works at full power, with an 3.0 rechargeble or primary cell it gives lower output.

Click to expand...

The KL4 uses a boost regulator and applying voltage that exceeds the Vf of the LED will cause it to go into direct drive mode. Two Li-Ions probably exceeds Vf of the LED even under load. 1.05A sounds like DD to me.

Ok... I'll check the current with primary cells today. But the L4 has the same brightness with primary cells and with these 3.0V RCR123s.
I have an Ansmann battery tester, which displays the voltage of a cell under load. When I test these 3.0V RCR123 cells, it show exactly 3.0V. Open circuit I measure a much higher voltage. That is what makes me so sure that these cells do not harm my L4.
I'll report back later.

As for runtime you can expect about 20-25 min. in regulation on a (3.7 volt) RCR123.

Jan

CM said:

When you say it gives lower output with primary cells

Click to expand...

It gives lower output with 1 primary cell on a VG FB1 or the E1L Body.
With an 3.7V RCR123 I reach the same brightness as with 2 primary cells in the L4 body.
Sorry for misleading...

Ok. I checked my L4 with 2 primary cells:
The first pair (Panasonic) were pretty depleted and measured around 2.5v. The measured current bounced up to 1.9A and then settled at 1.5A.
The second pair (Panasonic) was a little newer but not brand new (2.95v): The current stayed at 1.33A
Then I tried a brand new pair of Surefire CR123s, which measured 3.18V. The current started at 1.15A and raised to 1.28A within 30 seconds.

What I've learned: The current flowing inside a regulated light depends on the voltage provided by the batteries. A lower current can be indication to a higher batterie voltage, as far as the regulation circuit still works. Or it droped out of regulation, because of a too low voltage....

Does this make sense? :thinking: